The present invention relates to a system for monitoring and controlling a flexible roof assembly. More particularly, the present invention relates to a system for monitoring and controlling the height of a flexible roof system of the type normally used on covered sports stadiums, etc. Additionally, the present system includes a device for detecting any accumulation of ice or snow on the outer surface of the roof so that the ice or snow can be quickly eliminated.
Flexible roof assemblies have become somewhat common for sports stadiums in very recent years. Flexible roof assemblies for such stadiums are advantageous because of their lower installation costs, and because of the ability to cover larger areas than may be practically possible with rigid or structural type roofs. The principal advantage of a flexible roof system is that it does not require an elaborate rigid support system for supporting the roof. It will be understood that, in covered sports stadiums, the presence of any supporting structures for supporting the roof which extend into the interior of the stadium are undesirable. Therefore, the only practical alternatives for constructing a roof assembly for a large covered stadium which will have an unobstructed view for all attendees is to either provide a rigid roof assembly which is supported at its edges, or to provide a flexible roof system which is supported by air pressure within the stadium.
It will be understood that a rigid roof structure which spans the type of distances normally associated with large sports stadiums can be extremely complicated and extremely expensive. Because a flexible roof system is supported principally by a slight positive pressure within the stadium, the flexible roof need not be structurally rigid itself. In contrast, the typical flexible roof assembly cannot support itself in the absence of a required positive pressure within the stadium. This lack of structural rigidity eliminates the problems normally associated with constructing a rigid type of roof and greatly decreases the cost of such a roof.
A conventional flexible roof is maintained in position by constantly maintaining a positive pressure within the stadium with respect to the atmospheric pressure outside of the stadium Typically, one inch of positive pressure is normally maintained within the stadium with respect to the atmospheric pressure outside of the stadium to maintain such a flexible roof assembly in its proper orientation. It will be understood that the actual pressure within the stadium and the actual pressure exterior to the stadium are not critical, so long as the pressure differential between the inside and the atmosphere is maintained at the required difference such that a positive pressure is always maintained within the stadium.
Because of the necessity of maintaining the flexible roof at its proper height, it will be understood that monitoring systems are necessary to constantly monitor the pressure differential between the interior and atmospheric pressure. These monitoring systems are normally coupled to a system of fans or air handling units which are designed to introduce air into the structure to maintain the pressure differential, thereby maintaining the roof in the proper position. Normally, the system of fans includes a plurality of individually operating fans, which are sequentially placed into operation depending upon the signals received from the monitoring system. When the monitoring system detects a lower than required pressure differential, individual fans or pairs of fans are sequentially activated to increase the pressure within the structure. It will be understood that there are many variables which affect the pressure within the structure. Doors may be opened which can release a great amount of the pressure within the structure within a short period of time, creating a decrease in the required pressure differential. Additionally, temperature changes can result in pressure fluctuations which must be compensated for by the fan system.
Although the conventional monitoring systems are generally capable of controlling the fan system such that a desired pressure differential is maintained to keep the roof assembly in the proper position, it will be understood that by simply monitoring pressure differential, the actual height of the roof is not taken into consideration. Monitoring the pressure differential between the interior of the structure and the atmosphere is simply an indication of the position of the roof structure when all other conditions are normal. Under certain circumstances, the actual position of the roof could be considerably different than the indicated position of the roof relying solely upon the pressure differential. For example, if the roof structure accumulates a build-up of ice or snow, the weight of roof assembly will increase. This increased weight may cause the roof assembly to decrease in height. Using this example, by merely monitoring the pressure differential between the interior of the structure and the atmosphere, such a lowering in height of the roof would probably go undetected, at least for a period of time. Thus, with such conventional systems, the height of the roof can change somewhat without such a change being indicated by conventional pressure monitoring systems. Thus, it would be advantageous to provide a system for monitoring and controlling a flexible roof assembly which could determine and monitor the actual height of the roof assembly and utilize such actual height measurements to accurately control the roof.
It is therefore one object of the present invention to provide a flexible roof control system in which the actual height of the roof is used to control the input of air into the structure.
Another object of the present invention is to provide a flexible roof control system in which radar units are utilized to measure accurately the actual height of the roof.
Yet another object of the present invention is to provide a flexible roof control system in which an average actual height measurement is provided so that fluctuations in height of one section of the roof which are compensated for by opposite direction fluctuations of another section of the roof are averaged out.
Yet another object of the present invention is to provide a flexible roof control system which is capable of detecting accumulation of ice or snow on the outer surface of the roof before the accumulation becomes significant, with the system capable of distinguishing between ice and snow accumulation and simply water present on the roof.
According to the present invention, a system for monitoring and controlling the position of a flexible roof assembly of a building structure is provided. The system includes means for forcing air into the building structure to elevate the roof assembly and at least one echo ranging device for determining the actual height of at least one section of an inter portion of the roof assembly to produce an actual height measurement. The system also includes means for controlling the air forcing means in response to the actual height measurement of the at least one section of the roof assembly such that the position of the roof assembly is accurately controlled.
One feature of the foregoing structure is that the actual height of at least one section of the roof assembly is determined to produce an actual height measurement. One advantage of this feature is that, by monitoring the actual height of the roof, changes in the position of the roof are immediately detected and can be quickly controlled.
Another feature of the foregoing structure is that means for controlling the air forcing means are provided, with the controlling means being responsive to the actual height measurement of the roof assembly. One advantage of this feature is that the forcing means are directly controlled by controlling means in response to the actual height measurement of the roof assembly.
In preferred embodiments of the present invention, the system further includes means for detecting ice and snow accumulation on an outer surface of the roof assembly. One feature of the foregoing structure is that means are provided for specifically detecting ice and snow accumulation, with the means being able to distinguish between ice and snow accumulation and merely rain water accumulation. One advantage of the foregoing structure is that ice and snow accumulation on the roof assembly can be detected and controlled before such accumulation can build up to harmful levels.
Also in preferred embodiments of the present invention, there are a plurality of echo ranging devices, with each echo ranging device measuring the height of a designated section of the roof assembly, with calculating means being provided to calculate an average height of all of the designated sections of the roof assembly. The average height is then utilized to generate an average height signal. One feature of the foregoing structure is that multiple echo ranging devices are provided to measure the actual height of several designated, separate portions of the roof assembly, with an average height then calculated to produce an average height signal. One advantage of the foregoing structure is that, by producing an average height signal, normal fluctuations in the height of the roof which do not require an adjustment of the air input into the structure can be averaged out.
Also in preferred embodiments of the present invention, means for alternately activating each echo ranging device during separate distinct time periods such that only one echo ranging device is transmitting an echo signal during any one time period is provided. One advantage of the foregoing structure is that, by alternating the operation of the separate echo ranging devices, the potential for interference between the multiple echo ranging devices is eliminated.
Thus, the present invention provides a system for accurately monitoring and controlling the position of a flexible roof assembly by utilizing the actual height of the roof assembly as the controlling perimeter. By utilizing the actual height of the roof assembly, the position of the roof assembly can be maintained accurately, and small changes in the height of the roof assembly which can indicate a trend in movement of the roof assembly, can be detected immediately and compensated for. This system is a significant improvement over conventional systems which merely monitor the pressure differential between the interior of the structure relative to the atmosphere. Such conventional systems are incapable of detecting small changes in the position of the roof assembly which could indicate potentially dangerous trends in movement of the roof.
Additional objects, features, and advantages of the invention become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.